Color television system



A. VAFLGA COLOR TELEVISION SYSTEM- `2l Sheets-Sheet 2 j Filed sept." 13,1951

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SUPPLY NVENTOR .n F l AMPLIFIER l D ETECT' O FI CSCI LL TOR funAMPuFfsri z--osrecroR the case of they in front of thc tubo.

annessi A coton retevision: srsmrvr v Andrew Verga, Phl-iadclphinyla. Application September 13, 1951, ScrinlNo. 146,429

comme I (ci. 11s-5.4) v

This invention relatesvto a color television system and- -more particularly to apparatus and process for providing color television in a system which is compatible with present black and white receiving,7 equipment.

"In the field of color tems comprise thciCBS held-sequential system, the RCA dot-sequential system'and thcCTI line-sequential system. l t has been found that there are disadvantages inherent in each of theabovc systems.' The lacking in definition as compared to thcshow linctlicirer orv linecravrl which can bc eliminated only by making the system leven more complex. As in RCAlrsystcm, thcrc'is also required either a three gun 4system or a'l tri-color tube. I 'The principal. object of the present invention is to provide a color television system which will be thoroughly compatible with existing equipment and at the same time utilize the standard cathode lray tucc now employed in the standard black and white telcyisicnreceivcr regardless of size and eliminate mechanically positioned color 4iiltcrs lwhich 'become exceedingly bulky inrcc'eivers with large picture size. I

A further object of the prcsentinvention is -to prov-idc .a Acolor television system which may employ. a standard black and white receiver with the usual cathode ray tube without the necessity of any complex circuit changes and l provide n means for electrically sc-lcctinghie color scquenco--in synchronism with the transmitted signal.

A further object or the present invention isto provide an clcctrical'mcnns for sequentially ii'ltcring-fthe color'to be picked up by thc iconos'cope or camera tubo 4at the television trnxmnlittor.

'Means for attaining the abovestatcd objects are shown in the accompanying drawings in which Fig. 1 consists of a block diagram representation of the receiver circuit` used in carrying out the present invention in combination' with a cathode ray tube and a'colorselector plate mounted Figs. 2 and 3. show alternative forms of color selector plates.

ceivcr. l

Fig. 5 shows in dingrammnticalform the combination ot' the present inycntion in conjunction witha television television there have boen'a number' l of systems which have been proposed. The principal sys-y C BS'sysicm is substantiallyy standard bluck'.. and white system and is incompatible withprcsent black The RCA system overof definition inherent in the tri-color tube, neither of which at the receiving end f been shown.

tor unit which is made up shown in Fig. 1. The

`7. The plate 5 6 and 7 which are-practically integral with the plato 5 are one side as shown in Fig.

2i camera associated with the transmitting end of the teicvision system.

As shown in the drawings' the usual television receiver circuit is employed. in Fig. 1 the 'ulcer diagram starts I at the right hand side with the u suai rst detector and oscillator stage. Itwill'bc understood by those skilled in the art that the preceding stages will bc-the-samc as in standard telcvision'rcceivcrs andthcreforc these have not It should also be noted. that the sync scparator and tiltcr'is conncctcdinto the circuit in 'the standard way andftltat. the ,output'rozn the video amplifier is fed to the cathode ray tube 1 in the usual manner.' The horizontal dclectiort-v and vertical deflection amplifiers generation of'this sync pulse at the transmitting end is described at a later point in thissncciication; The output from the color selector amplifier is fed to the color sclc'cof three component parts as central portion of the color selclctor unit 4.ccnsists of a transparent plate S having on cach surface a very thin metallizcd conductive coating 6 and itself is' transparent and the thin .films also transparent. 'Pla-tes of thisnaturc, with coating on 43, are availcble commercially being similar to Pyrex `brand E-C Radio -Glass Panels' ianufacturctl and sold by the Corning Glass Works', Cornin'g,'New York, or a product known as NESA Coated'llate manufactured and sold by Pittsburgh Piate Glass Com- I where Ev-Potential ditfcr'cncc rx-'Change in wavelength Fig. 4 shows -an alternativo block ldiagram for thc re-y fraction effect' or, bircfrin g encc with' respect to the passage the color 1 are brought c pany, Pittsburgh, Pa. As shown in Fig. i'the output from selector amplifier is electrically connected to coated surface dond '7 of. the plate. 5 'by means of the contact stripll and the other coatcdsurfacc is connected to ground luy-means of contact strip 9. The other clemcnts'ofcolor selector-unit 5 comprise the plates 10 and llwhich in Fig. 1 are shown in an cxplodcdvicw.' 'lhcsc plates consist of a transparent piastic polarizing material such as the product known as Polaroid which is manufactured and sold hy thePolaroid Corporation,l vCambridge, Mass. in actual operation the plates 5, 1Q and 11 lonely together and thinly/*mounted in front of the viewing surface of thc cathode ray. tabel.

- It will be noted that the color selector anxrllicr is conne'ctcd to the high'vo'lt-agc power supply. Consequently the voltagewhich is applied to thc mctallicd coating 6 of plate 5 isla varia'oic highvoltage depending upon the particular sync pulse coming to thc color selector ampland depends greatly I- isthc lengthvof `path through the plate.

K- Kerr electro optic constant for materiall selected." order are -imprcsscdup'on plate Sv When voltages of this a difference 'Ofi electrical potential is produced between the two surfaces of the plate 5 which produces anclec trostatic stress' in the material resulting in a double rcr i ,tt s i "A This voltage is .correspond in time'with4 the particulancolor .mitted. Where these sync pulses are impressed on the video carrier they arev incorporatedr in Athesarne way as' the horizontal' and vertical delection sync pulses and the vcolor selector pulse transmitted Vis then separated out at 'facesof the color selector above ground.

which theelcctrically conductive material of producing differences in ray/.tube 1. The white light from cathode ray 'tube 1 s incident upon and passes throu'gh polarizcr 1'0 and is' plane polarized. Thepolarized lightthen passes through the' metallized conductive coating 6 ind'is doubly rev' fracted in plate-5 4and vpasses' through coating7 and the analyzerll which is rotated at 90 to' polarizer 30.

' Th'etlcgreeot stress rind hence the color-produced varies with the impressed voltage nnd'thcsc impressed vvoltages are selected to produce the colors red, blue-.and green when viewed through the polarizing plates l and 11.

. As shown .in Fig. l thepolarizing plate it) operates vas a polarizer andthe plate v11 operates as-an analyzer. The change in color o ccurs instantaneously on the change in theimpressed voltage and' consequently the problem ot rcproduetion'ofn television picture'in color reduces itself to applying the predetermined voltage to the plate in the proper time'sequcnce relative to.'the' transmission ol the video signal.

Therefore a'number of. known ways of transmitting-the video signal in such a Way as to'sueccssively transmit in,

the desired red, blue and green sequence.

ln theoperation of thc present system sync pulses are generated to being transthe sync separator and filter-as shown in Fig. l. hesc color selector sync pulses maycomprise three different pulses only one of which would he transmitted at a given timeor a'zpredetcrminedvoltage corresponding to one of the colors may be used' at the colorselector plate as a standard no pulse voltage in which case only two sync `pulses would be required to correspond with-'the-other t'wo 'of the remaining threel colors. of Figs. l 'and 4 show a connection the metallizcd surfaces, it will be While the drawings understood that lany arrangementl whereby V there is produced asubstantialjdif-V ference of potential as between the two' metallized sur magnitude of the voltage difference is such as to produce a stress in the transparent mctallized plate which will produce adouble refraction corresponding to the desired color when ultimately viewed through'the analyser. This difference of potential -may of course be produced 'either with one surface of the color selector' plate at ground or The. exact voltages for -the particular colors will fde'pend upon the composition of the plate on is deposited. This plate should 'be transparcntbut may borosilicate vglass such as Pyrex vglass No.l 7740 as manufactured by Corning Glass Wo'rksfor clear Bakelite -or other synthetic resins'. The coloret-:ieetis produced by the doubly retracted polarized light as fviewed through the analyzer element Changes in color are produced by setting-'up different stresses which in 4turn h'ave'the'eflect 'the' double-refraction.

An alternative arrangement for'the reception and use of sync pulses utilizing the aud-io carrier Ais shown in Fig.

" 4. ln this embodiment ofthe invention the desired color -selector'sync pulses are impressed onl the audio carrier at the transmitter by amplitude modulation andA in this separate fro-mthe-sync separator fonthe color selector.

Alternative forms of the plate. 5 are shown: inFigs. 2

and 43. ln the'form shown in Fig. 3 this plate consists of f a central plastic sheet 12 to which'there is attached on each surfacea metallize'd plate 13 and 14. Connections are'providccl to the metallizcd surface of the plates 13 l c. *N

to ground of one or"v plate vwill suffice providcd the way interference with `the. usual frequency modulated 'at the receiver just after the mixer as shown in Fig. 4,.

trostatically stressed material which'arc .and-15 es showin. ln the vbirefring/:nccoi isotropic` material of potential will permit the passageof the red, green andoneness form shown in Fig. 2 the central'plate is made up of 15 with contact strips 16 and 17. lThe effect of this arrangement is to produce a stress in each of the plates 15 and the combined effect of these stresses viewed edgewise through an analyzer endpolarizer provides the sante zcc ilor el lccttis inthe case of the comblnn-tlon-shown'in The electrically operated color filter receiving may also. be used at the television camera, as represented simply in Fig. 5.

entering lens It? passes through pola-rizer 23, lthrough metallized coating v21 and'isotropic material 2G. and metallized coating '22 through analyzer Ztlfandlens 19 and finally impingc on photosensitive material' in iconoscope in eiectrical'potcntial on metalli'zed coatings 2l and 22.

The electrical potential applied ts selected vto produce 'so .that three values blue components rcspectively'of the incident light from the 4sene being televised. The voltages are-sequentially applied and corresponding pulses are superimposed on the carrier'to bel'separated at the receiving end as previously described.

Although theinvention 'as described represents a method 'of color transmission and reception it .is 'understood that a reforming of parts or thefproduction of 'stresses -by mechanical means does not constitute a dev parture from the spirit of the-invention.- The 'foregoing description uses the electro-optic properties of the 'elecless complication that'the photoelastic properties set up by more veurnbers on'te mechanical devices.

lt is further understood that manualv adiustmenls are provided in the color selector amplifier for controlling the shading of each color.

1 .in a color tclevisionsystem the combination of a 'device having a surface on which an image is reproduced.

means for providing said device with image producing signals, a color selectorunit interposed in the 'external light pathof said device'comprisingpin combination, a

polarizer element, an` analyzer element and a stress rc-v sp'ortsive element mounted between said polarizer und said analyzer elements s aid'stress responsive element con- 4 sisting of a material which is substantially transparent to lighfunder no stress conditions but which vwhen under.

stress subjects polarized lightft'o double refraction on passing through said element thereby changing the color of'said polarized light as viewed" through an analyzer, electrically conductive layers in contact with the opposite surfaces of said v`stress responsiveelemen't, and means to apply successively a plurality of' different stress pro` ducing vol-tages to 'one of said electrically 'conductive layers thereby' causing said stress responsivev clementl to polarized -light passing therethrough, the extent of double refraction being 'such that' successive 'prcsclcctedcolors are produced Vby said vdouble -retraetion at the stress vresponsive element as viewed through the said analyzer.

52. A color television system including a device having a surface on which an -imagc is reproduced,v means for A providing said device with a plurality of-successive image' producing signals representing.predetermined color portions of subject matter being televised,- a color selector unit interposed 'in the external light path of said image producing device comprising a light polarizing member,

a plurality of metallizcd plates as described for obtained with light, emerging from v the a stress responsive, double reraeting element positioned Y l aruosa;

in cooperativerelationshipwith said light polarizing memher, n light polarizing analyzcrtelcment positioned in co- .operative relationship with said stressresponsive element said stress'responsivc element consisting of Aa .material which is substantially transparent to iight under no stress conditions but .which when under stress sulxisctspolnrizcd light to-doublc refraction Von passing through said element therebychanging the' color of said polariaed light as viewed through an analyzer, and means for applying successively a plurality of diterent voltages to said stress l.responsiveelement thereby causing said stress responsive velement to doubly retract polarized light passing therethrough, the extent of douhle retraction being lsuch that successive preselected colors are produced by'saiddoubie refraction at the stress lresponsive element as viewed through lthe said analyzer.

3. The invention of claim 2 further characterized by the fact that said stress responsive means ,coating in contact with the opposite face surfaees v4. The invention of claim.

glass .plate having a thin metallizecl'c'oating on its opposite face surfaces.

5. In a color television receiving system a cathode ray picture tube having a viewing surface, means to polarizc external viewing surface of said picture tube stress responsive, color producing, means for subjecting said'polarizcd light to double refraction,

analyzer means positioned in the lviewing path of .the

doubly retracted, polarized light, meanstor applying'suc.- eessivc diicrent voltages to said double refraction means whereby successive color changes are produced at the stress responsive unit as viewed through the analyzer.

6.Tl;fe invention o f claim 5 further characterized-by means for producing variations in 'said electrical potential in response '.to pulses synchronized with Vthe time at which a' particular color is being televised.

7. The invention ofelaim `2 further characterized ,by the fact that said stress' responsive means consists of a plurality of transparent plates positioned one ontop of consists of a' transparent plate having a thin electrically .conductive the other, each-plate hav-ing an electrically conductive.

metallized 'coating on the opposite face surface thereof.

-8. The invention of claim 2 further characterized by thefact that said stress responsive mea-ns consists of a tra spare-nt plastic plate in combination with two transparent plates itt-contact withl the opposite face surfaces thereof and having clectrically-conductive metallized surfaces .on the' faces disposed against' the tirs-t mentioned l y Z'futther characterized by the fact that said stress responsive means lconsists of a .tions but'whieh when underslress transparent plate. l

. 9. In a lcolorteicvision systein a lcombination of a television transmitter including an optical systcr-n in which is interposed 'aneiectrostatically operated color fitter consisting o'rpolarizer, analyzer and a material whose elcctrooptie birer'ringence is'rletcrrnined hy voltages applied' thezeto an'd a device at the receiving end of the system having a surfaceon which arrimage is reproduced, a color selector element interposed in the external light path of said device comprising-in'eornbination a .p Glarizer, an analyzerrand'a' stress responsive element, said stress responsive element consisting of a material which is substantially transparent to light under no stress condisubjects polarized light to double refraction on passing through said clement thereby chan-ging the'c'olor of said polarized-light as l viewed through an analyzer, electricaily-conductivelayers in contact'with the opposite surl't'acc 'of said stress rcsponsive element and-ineens ,for applying successively a plurality ofl varying' stress producing voltages toene of said electrically conductive layers thereby causing 'said stress responsive element todou'bly retract polarized light .passing therethrough, -the citent Aol double 'refraction being such that vsuccessive preselectedv eoiors are produced by said double refraction at the stress responsive element Aas viewed through the said analyzer.

References 'Cited inthe 'le of this patent uNrrso STATES PATENTS' 

